As a conventional mechanism to heat a substrate, PTL 1 has proposed a mechanism in which the substrate is heated while being supported by supporting pins integrated with a lifting device and being located closer to a heating plate. In the technique disclosed in PTL 1, the heating plate is placed in an upper part of a vacuum unit, and the lifting device including the supporting pins is provided under the heating plate. In the process of heating the substrate, the substrate is placed on the supporting pins, and then the lifting device is driven to raise the supporting pins, so that the substrate is located closer to the heating plate and is heated.
On the other hand, there is another proposition for fast heating that, in order to obtain uniform wafer temperature with a lamp heater, a ring-shaped component having a slightly larger diameter than that of the wafer (hereinafter, referred to as a guard ring) is provided to the periphery of the wafer (PTL 2). When the wafer is heated by a lamp located opposite to the wafer, the surface temperature of the wafer is normally highest at the wafer center, and radiant heat causes heat of the wafer release to the environment, so that the temperature is low at the outer edge. If the peripheral ring is provided, the wafer outer edge is integrally joined to the peripheral ring, and the heat radiation can be reduced. This can improve the uniformity of wafer temperature.
In the conventional technique, the guard ring is placed at a predetermined position in the apparatus, and each wafer to be processed is delivered by a delivery mechanism. The wafer and guard ring are located with a predetermined positional relationship, and lamp light is then projected to heat the wafer. The processed wafer is carried out in a similar manner. In the case of a heating process to heat wafers at multiple positions depending on various purposes, for example, the positional relationship between the peripheral ring and the wafer is changed among the positions (where the distance between the lamp and a wafer at irradiation is changed) in the above structure. If the position of the peripheral ring is changed to avoid the aforementioned situation, the mechanism must be complicated and, moreover a problem of reliability is caused.
The guard ring, which is used to obtain the uniformity of temperature of the heated wafer, is therefore desirably made of the same material as wafers. However, the guard ring is repeatedly used (heated) unlike wafers. Therefore, another durable material having thermal characteristics (the specific heat and thermal conductivity) close to the wafer is often selected for the guard ring.
One of the reasons thereof is that it is difficult to provide a forced cooling device for the guard ring because of the mechanical restriction. Especially in an apparatus for processing in vacuum, the absence of a cooling device leads to an undesired temperature increase of the guard ring, a temperature difference between the guard ring and the wafer before processing, and changes thereof with time, which could also influence the process. The guard ring is intended to prevent or reduce temperature increases and damages of components by not only providing uniformity in wafer temperature, but also blocking lamp light traveling toward a lower part of the chamber.